Copper-catalyzed mechanochemical click reactions using Cu(II), Cu(I) and Cu(0) catalysts have been successfully implemented to provide novel 6-phenyl-2-(trifluoromethyl)quinolines with a phenyl-1,2,3-triazole moiety at O-4 of the quinoline core. Milling procedures proved to be significantly more efficient than the corresponding solution reactions, with up to a 15-fold gain in yield. Efficiency of both solution and milling procedures depended on the p-substituent in the azide reactant, resulting in H < Cl < Br < I reactivity bias. Solid-state catalysis using Cu(II) and Cu(I) catalysts entailed the direct involvement of the copper species in the reaction and generation of highly luminescent compounds which hindered in situ monitoring by Raman spectroscopy. However, in situ monitoring of the milling processes was enabled by using Cu(0) catalysts in the form of brass milling media which offered a direct insight into the reaction pathway of mechanochemical CuAAC reactions, indicating that the catalysis is most likely conducted on the surface of milling balls. Electron spin resonance spectroscopy was used to determine the oxidation and spin states of the respective copper catalysts in bulk products obtained by milling procedures.

Novel O-alkylated quinoline and N-alkylated 4-quinolone derivatives attached to the ferrocene moiety through 4,1-(7a-d, 8a-d and 12a-d) and 1,4-disubstituted (9a, 9b, 10a and 10b) 1,2,3-triazole moiety were synthesized. The observed regioselectivity of O-vs. N-alkylation was explored by the use of NMR and computational techniques. Among the N-alkylated derivatives, the quinolone-ferrocene conjugate 9a displayed marked activities against chronic myeloid leukemia in blast crisis (K562) and Burkitt lymphoma (Raji). The 6-chloroquinolone-ferrocene conjugate 12c, with selective inhibitory activity on Raji cells and no cytostatic effect on normal MDCK1 cells was highlighted as the most promising anticancer organometallic complex in a group of O-alkylated quinolines.

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Mono-(3a-3e and 4a-4e) and bis-ferrocene (5a-5e and 6a-6e) conjugated 5-substituted uracil derivatives that are bridged by 1,2,3-triazole linker were synthesized. The impact of ferrocene unit and spacer between ferrocene and triazole on radical scavenging potency was observed. Bis-ferrocenyl uracil derivatives exhibited better antiproliferative activities than their monoferrocenyl analogs. Bis-ferrocenyl methyl-(5b) and halogen-substituted (5e, 6c, and 6d) uracil derivatives showed pronounced and selective cytostatic activities on colon adenocarcinoma (CaCo-2) and Burkitt lymphoma (Raji) cells, with higher potency and selectivity than the reference drug 5-fluorouracil. Generation of reactive oxygen species (ROS) in CaCo-2 and Raji cells when treated with compounds 5b, 5e, and 6d was observed. Bisferrocenyl 5-chlorouracil 6c induced significant disruption in mitochondrial membrane potential that is accompanied by activation of apoptosis in CaCo-2, Raji, and acute lymphoblastic leukemia (CCRF-CEM) cells, while 6d caused mitochondrial dysfunction and apoptosis induction in CaCo-2 and Raji cells. Potent antiproliferative activity of 6c and 6d could be associated with mitochondrial membrane potential disruption accompanied by apoptosis induction. Our findings highlighted 6c and 6d with potent and selective antiproliferative activity on CaCo-2, Raji, and CCRF-CEM cells that may be associated with targeting cancer cell mitochondria, as a molecular target.

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